Robot vacuum reports C18 and stops; may say 'Please check the main brush cover' or 'Main brush not installed'.

Safety first: Turn the robot OFF and flip it over.

• Remove and reinstall cover: Open the main brush cover, remove the brush, then reinstall the brush and close the cover firmly until it clicks.
• Inspect latches: Check that the plastic latches on the cover are not broken or bent.
• Clean sensor area: Wipe around the cover hinges and any visible switches or magnets.
• Test: Power on the robot and start a cleaning cycle.

If C18 persists: The main brush cover sensor or switch may be defective and require replacement.